Dispersions containing bicomponent fluoropolymer particles and use thereof

ABSTRACT

The present invention provides a method of preparing an aqueous dispersion of poly(perfluorovinyl ether) homopolymers. The present invention further relates to a method of making an aqueous fluoropolymer dispersion comprising bicomponent particles of poly(perfluorovinyl ether) homopolymers and a second fluoropolymer. The dispersions of the present invention may be used for rendering fibrous substrates oil repellent, water repellent and/or stain repellent without altering the looks and feel of the substrate.

FIELD OF THE INVENTION

The present invention relates to a method of preparing an aqueousdispersion of poly(perfluorovinyl ether) homopolymers. The presentinvention further relates to a method of making an aqueous fluoropolymerdispersion comprising bicomponent particles of poly(perfluorovinylether) homopolymers and a second fluoropolymer. The dispersions of thepresent invention may be used for rendering fibrous substrates oilrepellent, water repellent and/or stain repellent. The invention furtherrelates to fibrous substrates, in particular textiles, treated with thefluorochemical composition and to a method of treating the fibroussubstrate with the fluorochemical dispersions.

BACKGROUND

Compositions for making substrates, in particular fibrous substrates,such as textiles, oil- and water repellent have been long known in theart. When treating fibrous substrates and in particular textile such asapparel, it is a requirement that the textile retains its look and feelas much as possible. Therefore, the amount of composition that can beapplied in any treatment to provide repellency properties to thesubstrates is limited because large amounts would result in disturbingthe look and feel of the substrate and would make them useless for manyapplications. As a result, the composition used for treating thesubstrates need to be effective at low application levels.

Fluorochemical compounds have been well known as being highly effectivein providing oil and water repellency to substrates and in particulartextile substrates. The commercially available fluorochemicalcompositions can be applied at low levels and are generally effective inproviding the desired oil and water repellency properties at these lowlevels.

Fluorochemicals taught for treating textile include polymers based onvinyl ethers that have a perfluoroalkyl group. For example, U.S. Pat.No. 4,929,471 discloses the use of a copolymer of CH₂═CH—OR wherein Rmay represent a fluorinated group for treating polyester fabric duringits manufacturing process so as to produce a polyester fabric that hassimilar physical properties as silk or rayon.

U.S. Pat. No. 4,029,867 discloses to provide soil repellency and soilrelease properties to textile using a copolymer of maleic anhydride anda comonomer of the formula CH₂═CH—CH₂—O—R_(f) wherein R_(f) represents aperfluorinated group. A homopolymer of CH₂═CH—O—R_(f) is disclosed in DE1720799 and is mentioned to be suitable for rendering textile oil andwater repellent. The aforementioned fluorochemical compositions are allbased on fluorine containing polymers that do not have a fluorinatedbackbone.

Fluoropolymers having a fluorinated backbone such as for examplepolytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene(TFE), have been known for coating substrates to provide variousproperties to the substrate including repellency properties.Fluoropolymers have for example been coated on cookware to providedesired release properties thereto. Fluoropolymers having a fluorinatedbackbone are disclosed in U.S. Pat. No. 4,546,157, U.S. Pat. No.4,619,983, U.S. Pat. No. 4,766,190, U.S. Pat. No. 5,110,385, U.S. Pat.No. 5,969,066, U.S. Pat. No. 3,450,684, U.S. Pat. No. 4,035,565, U.S.Pat. No. 4,368,308, U.S. Pat. No. 4,418,186, U.S. Pat. No. 4,654,394,U.S. Pat. No. 4,840,998, U.S. Pat. No. 5,639,838 and U.S. Pat. No.3,136,745. However, to be effective as a repellent coating, it has beentaught to apply fluoropolymer coatings in high amounts. Such thickcoatings are however unsuitable for treating textiles as they change thelook and feel of the textile substrate substantially, i.e. to the extentsuch textiles are unsuitable for use in apparel. Sometimes, suchcoatings are subsequently subjected to a sintering step at hightemperatures that would generally destroy many of the fibrous substratesdesired for treatment.

EP 969 055 for example discloses an aqueous dispersion containing PTFEand a copolymer of TFE and a perfluorovinyl ether (PVE) for coatingsubstrates such as ceramics or to impregnate textile. However, theamount of fluoropolymer in the treatment solution is at least 25% byweight resulting in a fairly thick coating. Moreover, the coating issubjected to a sintering step at a temperature of 420° C. which woulddestroy many fibrous materials used for apparel.

U.S. Pat. No. 4,670,328 discloses aqueous dispersions of certaincopolymers of TFE and PVE for the impregnation of textiles. Again, thelevel of fluoropolymer applied in the impregnation is so large that thelook and feel of the textile is substantially affected. Accordingly, theimpregnated materials are generally only useful in specializedapplications such as dust free clothes or chemical resistant clotheswhere the appearance of the clothes is of secondary consideration.

EP 186186 discloses a curable fluoroolefin polymer for making coatingsthat have high weatherability and good repellency properties such aswater repellency, oil repellency and/or stain repellency. However, athick coating is apparently required to achieve these properties.

Fluorochemical compositions for rendering fibrous substrates oil- and/orwater repellent are described in Applicant's co-pending application U.S.Ser. No. 09/861,782 filed May 21, 2001. The compositions comprise up to4% by weight of a fluoropolymer having a fully- or partially fluorinatedbackbone and comprise repeating units of the fomula —CF₂—CFR_(f)—, whereR_(f) is a perfluorinated organic group having a chain length of atleast two atoms and having at least one carbon atom.

Although perfluorovinyl ether homopolymers have been prepared, andcopolymers of perfluorovinyl ethers have been used in textiletreatments, the difficulty in preparing perfluorovinyl etherhomopolymers have heretofore prohibited their use in textile treatments.It would thus be desirable to find alternative fluorochemicalcompositions that do not display many of the disadvantages of thefluorochemical compositions in the prior art. In particular, it would bedesirable to find fluorochemical compositions comprising perfluorovinylether homopolymers that are effective in providing oil and waterrepellency to a fibrous substrate, in particular a textile substrate,without substantially adversely affecting the appearance of the textile,i.e. such that the fibrous substrate is suitable for use in apparel.Preferably, the fluorochemical compositions are also capable ofproviding soil repellency and soil release properties to the fibroussubstrate. Desirably, the fluorochemical compositions will be moreenvironmental friendly and sufficiently stable to substantially avoidformation of low molecular weight fluorinated substances. Thefluorochemical compositions are preferably also compatible with commonlyused textile treatments and are preferably easy to apply by a customerin a reproducible and reliable way. Finally, the desired fluorochemicalcompositions are preferably capable of providing durable repellencyproperties to a fibrous substrate.

SUMMARY OF THE INVENTION

The present invention provides a method of making a poly(perfluorovinylether) homopolymer dispersion comprising the steps of:

a) pre-emulsifying an aqueous mixture of a perfluorovinyl ether in thepresence of a fluorochemical emulsifier to an average emulsion dropletsize of 1 micron or less, and

b) polymerizing said perfluorovinyl ether in the presence of afree-radical initiator at temperature and for a time sufficient toproduce particles of poly(perfluorovinyl ether).

The perfluorovinyl ether used in the present invention of claim 1 are ofthe formula: CF₂═CF—R_(f), wherein R_(f) represents a perfluorinatedorganic group having a chain length of at least 2 atoms and having atleast one carbon atom and at least one oxygen atom. The R_(f) group maybe a perfluoroalkoxy group, a perfluoroether group or aperfluoropolyether group.

The present invention further provides a method of making afluoropolymer dispersion comprising bicomponent particles comprising thesteps of:

a) pre-emulsifying an aqueous mixture of a perfluorovinyl ether monomerin the presence of a fluorochemical emulsifier to an average emulsiondroplet size of one micron or less, and

b) polymerizing said perfluorovinyl ether in the presence of afree-radical initiator at temperature and for a time sufficient toproduce particles of poly(perfluorovinyl ether),

c) subsequently adding at least one additional fluorinated co-monomerwithout additional fluorochemical emulsifier, and

d) further polymerizing the resulting mixture.

As used herein a “bicomponent particle” is a single particle of twodistinct fluoropolymers. The first fluoropolymer is a homopolymer of oneor more perfluorovinyl ether monomers. The second fluoropolymer may beany fluoropolymer comprising one or more fluoromonomers, such astetrafluoroethylene homo- or copolymers, vinylidene fluoride homo- orcopolymers, or hexafluoropropylene homo- or copolymers or perfluorovinylether homo- or copolymers. The bicomponent particle may comprise acore-shell, inverted core-shell, half-moon, or other morphologies.

In a further aspect, the present invention provides a fluoropolymerdispersion for rendering a fibrous substrate oil and/or water repellent.The fluorochemical dispersion may comprise particles ofpoly(perfluorovinyl ether) homopolymer or may comprise bicomponentparticles of poly(perfluorovinyl ether) homopolymer and a secondcomponent fluoropolymer.

In a still further aspect, the invention relates to a fluoropolymerdispersion that comprises a bicomponent particle comprising a firstpoly(perfluorovinyl ether) and a second fluoropolymer. The firstfluoropolymer consists essentially of repeating units corresponding tothe general formula:

wherein R_(f) represents a perfluorinated organic group having a chainlength of at least 1 oxygen atom and having at least one carbon atom.

Such dispersions of bicomponent particles have been found to beparticularly effective for the treatment of fibrous substrates. Inparticular it was found that the second fluoropolymer contributed to animprovement of the repellency properties often going beyond a mereaddition of the oil repellency properties of the fluoropolymers on theirown, particularly with an auxiliary component as described below.Accordingly, the cost of a fluorochemical treatment composition maythereby be lowered as the cost of the first poly(perfluorovinyl ether)homopolymer is generally higher than that of the second fluoropolymer.

The fluoropolymer dispersion of the present invention has been found tobe effective for providing oil repellency and/or water repellencyproperties to a fibrous substrate without substantially affecting theappearance thereof. Furthermore, the fluoropolymer dispersion may beproduced such that the amount of low molecular weight species (less than1000 g/mol) in the composition is low, e.g. not more than 0.5% byweight, preferably not more than 1000 ppm, or is even free of suchsubstances. Also, the fluoropolymer dispersions generally will have ahigh chemical stability such that the fluoropolymer dispersionsgenerally do not form low molecular weight fluorinated substances over along period of time. The fluoropolymer dispersion may further providesoil repellency as well as soil or stain release properties. With theterm soil and stain release is meant that a treated substrate thatbecomes soiled or stained can be more easily cleaned in for example ahome laundering than an untreated substrate that becomes soiled orstained. Soil/stain repellency on the other hand refers to the abilityto repel soil thereby reducing soiling or staining of the substrate.

The amount of the fluoropolymer in a treatment composition willtypically be selected in order to achieve the desired level offluoropolymer on the substrate to be treated. Typically the amount ofthe fluoropolymer in the treatment composition is not more than 4% byweight (based on the total weight of the composition), for examplebetween 0.01% by weight and 4% by weight, preferably between 0.05% and3% by weight. Higher amounts of the fluoropolymer can be used as well,particularly in cases where the uptake of the composition by the fibroussubstrate is low.

In a further aspect, the present invention relates to a treatment offibrous substrates with the above fluorochemical compositions. Thesubstrates so obtained generally have good repellency properties such asoil repellency, water repellency, soil repellency. Additionally, thetreated substrates may exhibit good or improved soil/stain releaseproperties as well.

In a still further aspect of the present invention there are providedfibrous substrates, in particular textiles, that have coated on at leastpart of at least one major surface, the fluoropolymer dispersion of theinvention. The amount of the fluoropolymer on such a treated fibroussubstrate should generally be less than 3% by weight based on the weightof the fibrous substrate so as to preserve the general look and feel ofthe substrate although the amount that can be applied without adverselyaffecting the look and feel of the substrate will depend on the natureof both the substrate as well as the fluorochemical composition used inthe treatment.

In yet another aspect, the invention relates to the use of afluoropolymer dispersion to impart oil repellency, water repellency,soil repellency and/or soil/stain release to a fibrous substrate withoutsubstantially affecting the look and feel of said fibrous substrate, thefluorochemical composition comprising a solution or dispersion of afluoropolymer having fully fluorinated backbone and comprising one ormore repeating units corresponding to the general formula:

wherein R_(f) represents a perfluorinated organic group having a chainlength of at least 1 oxygen atom and having at least one carbon atom. Bythe term “without substantially affecting the look and feel of saidfibrous substrate” is meant that the treated substrate does not differsubstantially in appearance from the untreated substrate such that thetreated substrate can be used without objection in applications such asfor example apparel, where the look and feel of the fibrous substrateare a major consideration for its use.

Finally, the invention relates to fluorochemical compositions thatcomprise a dispersion of the aforementioned fluoropolymer(s) and furtheran auxiliary component, generally a non-fluorinated organic compound,that is capable of further improving the water and/or oil repellencyand/or the soil/stain release properties of a fibrous substrate treatedwith the fluorochemical composition.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

Fluoropolymers for Use in the Fluorochemical Composition

The poly(perfluorovinyl ethers) for use in the fluorochemicalcomposition are polymers that have a fully fluorinated backbone. Theterm “fully fluorinated” includes polymers in which all hydrogen atomson the backbone have been replaced by fluorine as well as polymers inwhich all hydrogen atoms on the backbone have been replaced withfluorine and chlorine or bromine.

The fluoropolymer has one or more repeating units that correspond to thegeneral formula:

wherein R_(f) represents a perfluorinated (i.e. all hydrogen atoms havebeen replaced by fluorine atoms) organic group having a chain length ofat least 1 oxygen atom and including at least one carbon atom.Preferably the chain length of the perfluorinated organic group is atleast 3 atoms. A particularly preferred R_(f) group has a chain lengthof at least 4 atoms of which at least 3 are carbon atoms.

Examples of R_(f) groups include perfluorinated aliphatic groups thatcontain one or more oxygen atoms. The R_(f) group may in particular be alinear or branched perfluoralkoxy group, preferably, the perfluoroalkoxygroup will have between 1 and 6 carbon atoms and specific examplesinclude perfluorinated methoxy, ethoxy and n-propoxy groups. Stillfurther, the R_(f) group can be a perfluoropolyether which may be linearor branched. According to a preferred embodiment, the R_(f) groupcorresponds to the following general formula:

—O(R¹ _(f)O)_(n)(R² _(f)O)_(m)R³ _(f)  (II)

wherein R¹ _(f), R² _(f) each independently represents a linear orbranched perfluoroalkylene group having 1, 2, 3, 4, 5 or 6 carbon atoms,R³ _(f) represents a linear, branched or cyclic perfluoroalkyl grouphaving 1, 2, 3, 4, 5 or 6 carbon atoms and n and m each independentlyrepresents an integer of 0 to 10. Preferably, at least one of n and m isdifferent from 0. Particularly preferred R_(f) groups according toformula (II) include those in which m is 0, n is 1, R¹ _(f) is —CF₂CF₂—,—CF₂CF(CF₃)—, —CF(CF₃)CF₂— or —CF₂CF₂CF₂— and R³ _(f) represents alinear, branched or cyclic perfluoroalkyl group having 1 to 6 carbonatoms. A preferred R_(f) groups according to formula (II) includes inparticular a perfluoropropyl group and those in which both m and n are0. Another preferred R_(f) group according to formula (II) includes inparticular a perfluoropropyl group and those in which the sum of m and nis 1.

It will be understood by one skilled in the art that the fluoropolymerof the fluorochemical composition may comprise a mixture of repeatingunits according to formula (I). For example, the fluoropolymer maycomprise a mixture of repeating units in which the R_(f) groupscorrespond to formula (II) above such as for example a mixture of arepeating unit corresponding the formula:

and a repeating unit corresponding to the formula:

or a mixture of repeating units derived from a combination ofperfluoro(propyl vinyl) ether and a monomer of the formulaCF₂═CF—O—CF₂CF(CF₃)—O—CF₂CF₂CF₃.

The repellency properties that can be achieved by the fluorochemicalcomposition largely depend on the presence in the fluoropolymer ofperfluorovinyl ether repeating units according to formula (I). Afluoropolymer containing only repeating units according to generalformula (I) has been found to yield excellent repellency properties on afibrous substrate treated therewith. Although higher amounts of therepeating units of formula (I) will generally improve performance, thecost of the fluoropolymer thereby also increases as well because themonomers from which these repeating units are derived are generallyexpensive.

In a particular embodiment of the present invention, the fluorochemicalcomposition comprises a fluoropolymer dispersion comprising bicomponentparticles of a first poly(perfluorovinyl ether) homopolymer and secondfluoropolymer each having a fully- or partially fluorinated backbone. Itis believed that the bicomponent particles are a core-shell polymercomprising a core of poly(perfluorovinyl ether) homopolymer and a shellof a second fluoropolymer.

The first fluoropolymer consists essentially of one or more repeatingunits corresponding to the general formula (I) set forth above.Generally the second fluoropolymer contains the repeating units offormula (I) in a total amount of not more than 50 mole %. The amount ofrepeating units in the second fluoropolymer may even be less, forexample not more than 25 mole % or not more than 10 mole %. Further,even if less than 1 mole % or substantially no repeating units arepresent in the second polymer, beneficial effects of the second polymerhave been noticed. In particular, it was noticed that although thesecond fluoropolymer generally does not (e.g. if it does not contain therepeating units of formula (I)) or only to a limited extent providesrepellency properties when used on its own, the second fluoropolymer isnevertheless capable of improving the repellency performance when usedin a dispersion of bicomponent particles with the first fluoropolymer.

Generally, any ratio of first to second fluoropolymers can be used toprepare the emulsion and the optimal ratio will depend on the nature ofthe fluoropolymers used in the mixture, the nature of the fibroussubstrate, amount of the mixture applied and level of repellencydesired. The optimal ratio can easily be determined through routineexperimentation. Generally, the weight percent of the firstfluoropolymer will be between 1 to 75 wt. %, preferably between 25 to 50wt. %, with the second fluoropolymer providing the balance. Thus,mixtures that are rich in the second fluoropolymer (have a weightpercent of second fluoropolymer of 50% or more), which contains no orlittle of the repeating units of formula (I), have been found to yieldgood repellency properties. Generally however, the total amount ofrepeating units according to the general formula (I) in such mixturesshould be at least 10 wt. %, preferably at least 20 wt. % to achievegood levels of repellency.

The bicomponent or core-shell particle dispersion may be prepared by thesteps of:

1) polymerizing an aqueous emulsion of monomers of the formula:

CF₂═CF—R_(f),

wherein R_(f) represents a perfluorinated organic group having a chainlength of at least 2 atoms and having at least one carbon atom and oneoxygen atom; in the presence of a free radical initiator and aemulsifier at temperature and for a time sufficient to produce particlesof poly(perfluorovinyl ether),

2) subsequently adding at least one additional fluorinated co-monomerwithout additional fluorochemical emulsifier, and

3) further polymerizing the resulting mixture.

Preferably, the emulsion of step 1) comprises droplets having an averagedroplet size of less than 1 micron, preferably 300 nanometers.

An important benefit of the use of a fluoropolymer mixture is that thetotal cost of the treating composition can be reduced while stillachieving a high level of performance, as the cost of perfluorovinylether monomers considerably exceeds that of other monomers that may beused in the second stage of the polymerization process.

The second fluoropolymer component of the bicomponent particle comprisesa homo- or copolymer of at least one ethylenically-unsaturatedfluoromonomer containing at least one fluorine atom substituent on adouble-bonded carbon atom, and further substituted with a halogen atomsuch as fluorine, chlorine, or bromine; hydrogen, or a lower fluoroalkylradical.

Useful fluorinated comonomers of the second component fluoropolymerinclude homo- and copolymers of tetrafluoroethylene, vinylidenefluoride, hexafluoropropene, chlorotrifluoroethylene,2-chloropentafluoropropene, 1-hydropentafluoropropene,dichlorodifluoroethylene, trifluoroethylene, 1,1-chlorofluoroethylene,trichloroethylene, and the like and optionally a monomer correspondingto formula (1) above.

Generally, the fluoropolymer will contain between 0 and 70 mole %,preferably between 0 and 60 mole %, more preferably between 0 and 40mole % of repeating units derived from tetrafluoroethylene, between 0and 95 mole %, preferably between 20 and 80 mole %, more preferablybetween 30 and 75 mole % of repeating units derived from vinylidenefluoride, between 0 and 95 mole %, preferably between 20 and 80 mole %,more preferably between 30 and 75 mole % of repeating units derived fromhexafluoropropene, whereby the total amount of repeating units derivedfrom vinylidene fluoride, hexafluoropropene and tetrafluoroethylene isgenerally between 0 and 95 mole %, preferably between 20 and 90 mole %,more preferably between 30 and 90 mole %.

The second component fluoropolymer of the fluorochemical compositioncontain further repeating units derived from non-fluorinated monomers.Examples of non-fluorinated monomers include alpha-olefin hydrocarbonssuch as ethylene and propylene. The amount of such further repeatingunits may vary widely and can be from 0 mole % to 50 mole % for anyparticular non-fluorinated monomer.

Specific examples of second component fluoropolymers that can be used inthe fluorochemical composition of this invention are copolymers oftetrafluoroethylene and a perfluorovinyl ether such as perfluoro(methylvinyl) ether, perfluoro(methoxyethyl vinyl) ether, perfluoro (propylvinyl) ether (PPVE-1), perfluoro (2-(n-propoxy)propyl vinyl) ether(PPVE-2) and perfluoro(ethoxyethyl vinyl) ether, copolymers oftetrafluoroethylene, hexafluoropropylene and a perfluorovinyl ether suchperfluoro(methyl vinyl) ether, perfluoro(methoxyethyl vinyl) ether,PPVE-1, PPVE-2 and perfluoro(ethoxyethyl vinyl) ether, copolymers ofvinylidene fluoride and a perfluorovinyl ether such as perfluoro(methylvinyl) ether, PPVE-1, PPVE-2, perfluoro(methoxyethyl vinyl) ether andperfluoro(ethoxyethyl vinyl) ether, copolymers of vinylidene fluoride,tetrafluoroethylene and a perfluorovinyl ether such as perfluoro(methylvinyl) ether, perfluoro(methoxyethyl vinyl) ether, PPVE-1, PPVE-2, andperfluoro(ethoxyethyl vinyl) ether, copolymers of vinylidene fluoride,hexafluoropropylene and a perfluorovinyl ether such as perfluoro(methylvinyl) ether, PPVE-1, PPVE-2, perfluoro(methoxyethyl vinyl) ether andperfluoro(ethoxyethyl vinyl) ether and copolymers of vinylidenefluoride, tetrafluoroethylene, hexafluoropropylene and a perfluorovinylether such as perfluoro(methyl vinyl) ether, PPVE-1, PPVE-2,perfluoro(methoxyethyl vinyl) ether and perfluoro(ethoxyethyl vinyl)ether.

Method of Making the Fluoropolymers

The poly(perfluorovinyl ether) homopolymer particles are producedthrough aqueous emulsion polymerization of a pre-emulsion comprising theperfluorovinyl ether monomer and fluorinated emulsifier wherein theaverage droplet size of the pre-emulsion is one micron or less,preferably 300 nanometers or less. In the aqueous emulsionpolymerization, the monomers are polymerized in the aqueous phase in thepresence of a free radical initiator and a fluorinated emulsifier,preferably a non-telogenic emulsifier.

Generally the time required for the homopolymerization is 6 to about 48hours and the temperatures ranges from 40 to 80° C., preferably 40 to60° C. Higher temperatures may lead to destabilization of the droplets.

The fluorochemical emulsifier will generally be used in amounts lessthan 1% by weight, for example from 0.1 to 1% by weight based on theweight of the aqueous phase. Examples of fluorinated emulsifiers includesalts, in particular ammonium salts of linear or branched perfluoroalkyl containing carboxylic and sulphonic acids having 4 to 11 carbonatoms in the alkyl chain. Specific examples include perfluorooctanoicacid ammonium salt (APFO, described in U.S. Pat. No. 2,567,011)C₈F₁₇SO₃Li which is commercially available from Bayer AG, C₄F₉SO₃Li andC₄F₉SO₃K (described in U.S. Pat. No. 2,732,398). A further example of aperfluoroalkyl containing carboxylic acid salt is C₈F₁₇SO₂N(C₂H₅)CH₂COOK(described in U.S. Pat. No. 2,809,990). Still further emulsifiers thatcan be used include perfluoropolyethercarboxylate emulsifiers such asdisclosed in EP 219065

In accordance with an embodiment of the present invention, the emulsionpolymerization may be conducted using a fluorinated emulsifier having amolecular weight of at least 200 g/mol, preferably at least 1000 g/molfor example by using a polymeric fluorinated emulsifier. Examples ofsuitable fluorinated polymeric or high molecular weight emulsifiersinclude perfluoropolyethers having one or more hydrophilic groups, inparticular ionic groups such as carboxylic acid groups or salts thereof.Examples of perfluoropolyether emulsifier include those according to thefollowing formulas (IV) or (V):

R_(f) ^(a)—O—(CF₂)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q¹-COOM  (IV)

MOOC-Q¹-O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q²-COOZ  (V)

wherein k, p and q each represent a value of 0 to 15, typically 0 to 10or 12 and the sum of k, p and q being such that the average molecularweight is at least 200 g/mol, preferably at least 1000 g/mol, R_(f) ^(a)represents a perfluoroalkyl group of 2 to 4 carbon atoms, M and Z eachindependently represent hydrogen or a cation, preferably a monovalentcation such as ammonium or an alkali metal ion and Q¹ and Q² eachindependently represents —CF₂— or —CF(CF₃)—.

Examples of fluorinated compounds useful as emulsifiers of formula (IV)include those corresponding to the general formula:

R_(f) ^(a)—O—(CFXCF₂O)_(r)—CFX—COOM  (VI)

wherein R_(f) ^(a) and M have the meaning as defined in formula (IV), Xis a hydrogen atom or a fluorine atom and r has a value of 2 to 15.Examples of such fluorinated emulsifiers are disclosed in EP 219065.Commercially available fluorinated compounds according to formula (IV)or (V) include FLUOROLINK™ C available from Ausimont SpA, KRYTOX™ 157FSL, KRYTOX™ 157 FSM and KRYTOX™ 157 FSH, all available from E.I. Dupontde Nemours and Company.

Still further fluorinated polymeric compounds useful as emulsifiersinclude the perfluoropolymers that comprise repeating units derivablefrom a monomer of the formula:

wherein s is 0, 1 or 2, and t is an integer of 2 to 4, and G is a moietycontaining one or more hydrophilic groups, such as a nonionic, anionicor cationic group. Examples of suitable nonionic groups include: —SO₂F;hydroxyalkylene, e.g., —(CH₂)_(n)OH where n is an integer of 1 to 18;hydroxyarylene; and an ester, e.g., —COOR, wherein R is an alkyl groupof 1 to 3 carbon atoms. Examples of suitable anionic groups include:carboxyl groups, e.g., —CO₂M where M may be hydrogen, a mono or divalentmetal ion (e.g., sodium, potassium or magnesium), ammonium (e.g., simpleammonium, tetraalkylammonium, tetraarylammonium) or phosphonium (e.g.,tetraalkylphosphonium); or sulfonate groups, e.g., —SO₃M, where M isdefined as above. Examples of suitable cationic groups includealkylammonium groups, (e.g., —(CH₂)_(n)NR₃ ⁺Cl⁻ where R may be hydrogen,alkyl or aryl).

Preferably, the fluorinated polymeric emulsifier is a copolymer oftetrafluoroethylene and a monomer according to formula (VII). Suchcopolymers and their method of making are disclosed in for example U.S.Pat. No. 5,608,022 and WO 00/52060. Suitable fluorinated polymericcompounds useful as emulsifiers are available as Nafion™ superacidcatalysts (e.g., Nafion™ SE10172) from E. I duPont de Nemours & Co.,Wilmington, Del. and are also available as Flemion™ superacid polymersfrom Asahi Chemical Co., Osaka, Japan and as Acipex™ superacid polymersfrom Asahi Glass Co., Tokyo, Japan.

If desired, several methods may be used to recover and recycle thefluorinated emulsifiers used in the aqueous emulsion polymerization.Such methods are disclosed in e.g. EP 524585, EP 566974, EP 632009, EP731081, WO 99/62858, WO 99/62830 and DE 19932771. Any of these methodsmay advantageously be practiced in this invention to remove and orminimize any remaining fluorinated emulsifier subsequent to the emulsionpolymerization.

According to a particular embodiment for making the fluoropolymerdispersions, the liquid perfluorovinyl ether monomer used in thepolymerization is pre-emulsified prior to its homopolymerization. Thepresent method allows the preparation of perfluorovinyl etherhomopolymers much more efficiently than the processes of the prior art.By the term “pre-emulsified” in connection with the present invention ismeant that the fluorinated monomer is emulsified in water to a dropletsize of one micron or less, preferably 300 nm or less, with the aid ofthe fluorinated emulsifier prior to polymerization of the liquidfluorinated monomer. The temperature of the polymerization to prepare anemulsion of perfluorovinyl ether homopolymer is generally between 40 and100° C., preferably between 50 and 80° C.

The perfluorovinyl ether monomer can be emulsified in water with the aidof a fluorinated emulsifier such as described above, prior to itspolymerization with the other monomers. The pre-emulsification of theliquid fluorinated monomer results in an emulsion having monomerdroplets. The pre-emulsion average droplet size can range from anaverage diameter of 1 μm or less, down to about 150 nm or even lower.Preferably the average droplet diameter is not more than 300 nm. Theaqueous emulsion should preferably have a pot life (settling time) of atleast 1 hour, more preferably at least 3 hours. The pot life or settlingtime is defined as the time required for 10% by weight of the monomerdroplets to settle or separate out of the aqueous emulsion. Droplet sizemay be determined, for exampled, by light scattering experiments as areknown in the art.

Aqueous emulsions of the perfluorovinyl ether monomer can convenientlybe obtained by suitable emulsification equipment such as for examplehigh speed rotor-stator mixers such as an Ultra-Turrax (Ika). Thestirring rates should be sufficiently high to achieve the desired degreeof emulsification and stability. Generally, stirring rates of 24 000 rpmor more can be employed. Air is preferably excluded during theemulsification. The pre-emulsion particle size can be further reducedwith high pressure homogenizers, available from APV Gaulin orMicrofluidics.

The amount of fluorinated emulsifier used to emulsify liquid fluorinatedmonomer is generally between 0.01 and 15% by weight based on the weightof the liquid fluorinated monomer, preferably 0.1 to 4% by weight.Although higher amounts of emulsifier can be used, they will notnecessarily lead to a significant increased pot life of the aqueousemulsion of liquid fluorinated monomer produced. In the two-step processfor making the bicomponent particle emulsion, lesser amounts my be used.

In the two-stage process of the invention, where a dispersion ofbicomponent particles are prepared, the pre-emulsion is firstpolymerised to a degree of conversion of at least 1%, preferably atleast 5%, as described, to produce a dispersion of perfluorovinyl etherhomopolymer particles and unconverted perfluorovinyl ether monomer (ifany). Additional fluorinated monomers are added with continuousagitation while the second stage of polymerization proceeds. The secondstage of polymerization should occur without additional fluorinatedemulsifier. In the absence of additional emulsifier, a bi-componentparticle dispersion is produced and the additional charge of fluorinatedmonomers are polymerized on the surface of the perfluorovinyl etherhomopolymer particles. Were additional fluorinated emulsifier to beadded, a mixture of discreet particles would be produced; a firstparticle of perfluorovinyl ether homopolymer and a second particle offluoropolymer derived from the additional fluorinated monomer feed atthe second stage of polymerization.

In the two-stage polymerization process (to produce the bicomponentdispersion) the polymerization may be initiated at a first temperaturefor the first stage of polymerization and at a second temperature forthe second stage of polymerization. The initial period will typically bebetween 1 and 6 hours, for example between 1 and 4 hours from the startof the polymerization reaction. If desired, further initiator may beadded during the polymerization but this may not be required. Amounts ofinitiator in the initial charge are generally between 0.01 and 2.0% byweight, preferably between 0.1 and 1.8% by weight, more preferablybetween 0.3% and 1.6% by weight based on the total weight of polymer tobe produced. The temperature for use at the initial stage (when a highertemperature is used) is generally between 40° C. and 100° C., preferablybetween 50° C. and 80° C. The temperature during the course ofpolymerization is generally in the range of 30° C. to 80° C. The optimalconditions can be readily determined by routine experimentation.

Actinic radiation may be used, instead of free radical initiators, toinitiate the polymerization. When actinic radiation, such as UV, is usedto initiate the polymerization, lower temperatures from about 0° C. toambient may used.

The aqueous emulsion polymerization of the perfluorovinyl ether can becarried out continuously in which, for example, a pre-emulsion ofperfluorovinyl ether monomers, water, fluorochemical emulsifiers,buffers and initiators are fed continuously to a stirred reactor underoptimum pressure and temperature conditions while the resultingdispersion or suspension is removed continuously. An alternativetechnique is batch or semibatch (semi-continuous) polymerization byfeeding a pre-emulsion of the ingredients into a stirred reactor andallowing them to react at a set temperature for a specified length oftime until a desired amount of polymer is formed.

In the second stage of the polymerization, the dispersion ofpoly(perfluorovinyl ether) is provided with the additionalfluoromonomers in a continuous or batch mode.

The polymerization can be carried out in a standard or conventionalvessel used for emulsion polymerization, but a pressure vessel isgenerally required for the second stage where gaseous fluorinatedmonomers are charged.

For the free-radical polymerization use may be made of any suitableinitiator or any suitable initiator system, for example ammoniumpersulfate (APS), or of redox systems, such as APS/bisulfite, potassiumpermanganate or actinic radiation such as UV light. If oil-solubleinitiators are used in the polymerization, it is generally preferred forthese to be mixed with the aqueous emulsion of the perfluorovinyl ethermonomer. For the purposes of the present invention, oil-solubleinitiators are those which have no, or only insufficient, solubility inwater. Examples of oil-soluble initiators are substituted dibenzoylperoxides and cumene hydroperoxides, in particular bisperfluoropropionylperoxide. For the first stage of the polymerization, persulfates arepreferred.

Water-soluble thermal initiators useful in the present invention areinitiators that, on exposure to heat, generate free-radicals whichinitiate polymerization of the monomers comprising the droplets of theemulsion. Suitable water-soluble thermal initiators include but are notlimited to those selected from the group consisting of potassiumpersulfate, ammonium persulfate, sodium persulfate, and mixturesthereof; and oxidation-reduction initiators such as the reaction productof the above-mentioned persulfates and reducing agents such as thoseselected from the group consisting of sodium metabisulfite and sodiumbisulfite. The preferred water-soluble thermal initiator is ammoniumpersulfate. Preferably, most water-soluble thermal initiators are usedat temperatures of from about 50° C. to about 70° C., while theoxidation-reduction-type initiators are preferably used at temperaturesof from about 25° to about 50° C. Water-soluble thermal initiatorscomprise from about 0.01 to about 2 weight percent, preferably about 0.1to about 2 weight percent based on the total weight of monomers in theemulsion.

The amount of oxidizing agent added in the initial charge is typicallybetween 10 and 10000 ppm. The amount of reducing agent in the initialcharge is typically also between 10 and 10000 ppm. At least one furthercharge of oxidizing agent and reducing agent is added to thepolymerization system in the course of the polymerization. The furtheraddition(s) may be done batchwise or the further addition may becontinuous.

The resultant fluoropolymer particles may be used as a dispersion perse. The particles may also be isolated from the aqueous medium byfiltration, coagulation spray drying, extraction into an organicsolvent, or other other techniques such as are known in the art.

The polymerization systems may comprise auxiliaries, such as buffersand, if desired, complex-formers or chain-transfer agents.

Fluorochemical Compositions

The fluorochemical composition comprises an aqueous dispersion of thefluoropolymer (whether perfluorovinyl ether homopolymer particles or thebicomponent particles). Generally, the amount of fluoropolymer containedin the treating composition is between 0.01 and 4% by weight, preferablybetween 0.05 and 3% by weight based on the total weight of thefluorochemical composition. Higher amounts of fluoropolymer of more than4% by weight, for example up to 10% by weight may be used as well,particularly if the uptake of the fluorochemical composition by thesubstrate is low. Generally, the fluorochemical treating compositionwill be prepared by diluting a more concentrated fluorochemicalcomposition to the desired level of fluoropolymer in the treatingcomposition. The concentrated fluorochemical composition can contain thefluoropolymer in an amount of up to 70% by weight, typically between 10%by weight and 50% by weight.

When the fluorochemical composition is in the form of a dispersion inwater the volume average particle size of the fluoropolymer particles isgenerally not more than 300 nm, preferably between 50 and 200 nm.

The dispersion may be additionally stabilized using non-fluorinatedsurfactants, such as non-ionic polyoxyalkylene, in particularpolyoxyethylene surfactants, anionic non-fluorinated surfactants,cationic non-fluorinated surfactants and zwitterionic non-fluorinatedsurfactants. Specific examples of non-fluorinated surfactants that canbe used are nonionic types such as Emulsogen EPN 207 (Clariant) andTween 80 (ICI), anionic types such as lauryl sulfate and sodium dodecylbenzene sulfonate, cationic types such as Arquad T-50 (Akzo), Ethoquad18-25 (Akzo) or amphoteric types such as lauryl amineoxide and cocamidopropyl betaine. The non-fluorinated surfactant is preferably present inan amount of about 1 to about 25 parts by weight, preferably about 2 toabout 10 parts by weight, based on 100 parts by weight of thefluorochemical composition.

Alternatively, a solution or dispersion of the fluoropolymers in anorganic solvent can be used as the fluorochemical treating composition.Suitable organic solvents include alcohols such as isopropanol, methoxypropanol and t-butanol, ketones such as isobutyl methyl ketone andmethyl ethylketone, ethers such as isopropylether, esters suchethylacetate, butylacetate or methoxypropanol acetate or (partially)fluorinated solvents such as HCFC-141b, HFC-134a, HFE-7100, HFE-7200 orperfluoroketones. HFE-7100, HFE-7200 and perfluoroketones arecommercially available from the 3M Company, St. Paul, Minn.

The fluorochemical composition may contain further additives such asbuffering agent, agents to impart fire proofing or antistaticproperties, fungicidal agents, optical bleaching agents, sequesteringagents, mineral salts and swelling agents to promote penetration. It isparticularly preferred to include one or more auxiliary components otherthan the fluoropolymer and that are capable of further improving theoil- and/or water repellency properties of a fibrous substrate treatedwith the fluorochemical composition or that are capable of improving thesoil/stain release properties of a fibrous substrate treated with thefluorochemical composition. Preferably, the auxiliary components arecapable of improving the durability of the repellency properties and/orsoil/stain release properties.

The auxiliary components are generally non-fluorinated organic compoundsand are also called extenders hereinafter. Suitable extenders capable ofimproving the oil- and/or water repellency properties include forexample blocked isocyanates including aromatic and aliphatic blockedisocyanates, aliphatic polyisocyanates and aromatic or aliphaticcarbodiimides including aromatic or aliphatic polycarbodiimides.Auxiliary components that are capable of enhancing the soil/stainrelease properties are generally non-fluorinated organic compounds suchas for example blocked isocyanate compounds that include apolyoxyalkylene group, in particular a polyoxyethylene group. Auxiliarycomponents that are generally capable of improving durability of therepellency properties or soil/stain release properties includenon-fluorinated organic compounds that have one or more groups (or aprecursor thereof) capable of reacting with the surface of the fibroussubstrate. Examples thereof include compounds that have isocyanategroups or blocked isocyanates.

Method of Treatment of the Fibrous Substrates

In order to affect treatment of the fibrous substrate the fibroussubstrate is contacted with the fluoropolymer dispersion of theinvention. For example, the substrate can be immersed in thefluorochemical treating dispersion. The treated substrate can then berun through a padder/roller to remove excess fluorochemical compositionand dried. The treated substrate may be dried at room temperature byleaving it in air or may alternatively or additionally be subjected to aheat treatment, for example, in an oven. This heat treatment istypically carried out at temperatures between about 50° C. and about190° C. depending on the particular system or application method used.In general, a temperature of about 120° C. to 170° C., in particular ofabout 150° C. to about 170° C. for a period of about 20 seconds to 10minutes, preferably 3 to 5 minutes, is suitable. Alternatively, thechemical composition can be applied by spraying the composition on thefibrous substrate.

The amount of the treating composition applied to the fibrous substrateis chosen so that a sufficiently high level of the desired propertiesare imparted to the substrate surface without substantially affectingthe look and feel of the treated substrate. Such amount is usually suchthat the resulting amount of the fluoropolymer on the treated fibroussubstrate will be between 0.05% and 3% by weight based on the weight ofthe fibrous substrate. The amount that is sufficient to impart desiredproperties can be determined empirically and can be increased asnecessary or desired.

Fibrous substrates that can be treated with the fluorochemicalcomposition include in particular textile. The fibrous substrate may bebased on synthetic fibers, e.g. polyester, polyamide and polyacrylatefibers or natural fibers, e.g. cellulose fibers as well as mixturesthereof. The fibrous substrate may be a woven as well as a non-wovensubstrate.

The invention will now be further illustrated with reference to thefollowing examples without the intention to limit the invention thereto.All parts and percentages are by weight unless stated otherwise.

EXAMPLES

Formulation and Treatment Procedure

Treatment baths were formulated containing a defined amount of thefluoropolymer treatment agent. Treatments were applied to the testsubstrates by padding to provide a concentration as indicated in theexamples (based on fabric weight and indicated as SOF (solids onfabric)). The samples are dried and cured at a temperature of 300° F.for ten minutes. The substrate used for the evaluation of treatments ofthis invention was 100% cotton US-3: cotton available from Test Fabric,USA. After heat cure, the substrates were tested for their oilrepellency properties.

Test Method for Oil Repellency (OR)

The oil repellency of a substrate was measured by the AmericanAssociation of Textile Chemists and Colorists (AATCC) Standard TestMethod No. 118-1997, which test was based on the resistance of a treatedsubstrate to penetration by oils of varying surface tensions aftercontact for 30 seconds. Treated substrates resistant only to Kaydol®mineral oil (the least penetrating of the test oils) were given a ratingof 1, whereas treated substrates resistant to n-heptane (the mostpenetrating, lowest surface tension test liquid) were given a rating of8. Other intermediate values were determined by use of other pure oilsor mixtures of oils, as shown in the following table. A “-” signfollowing a value indicates subjective determination by the rater of avalue intermediate between two values (i.e. 4- indicates a value between3 and 4)

Standard Test Liquids AATCC Oil Repellency Rating Number Compositions 1Kaydol ® 2 Kaydol ®/n-Hexadecane 65/35 3 n-Hexadecane 4 n-Tetradecane 5n-Dodecane 6 n-Decane 7 n-Octane 8 n-Heptane

Glossary Table Descriptor Structure and/or Chemical DescriptionAvailability Ammonium (NH₄)₂S₂O₈ Sigma-Aldrich, persulfate Milwaukee, WIFLUOROLINK ™ Perfluoropolyether macromer functionalized Ausimont, C withcarboxylic acid groups Thorofare, NJ HFP Hexafluoropropene; CF₂═CFCF₃Dupont, Wilmington, DE NAFION SE10172 Perfluorosulfonicacid/Polytetrafluorethylene DuPont, copolymer Wilmington, DE PBSPotassium perfluorobutanesulfonate 3M, St Paul, MN PPVE-1Perfluoropropyl vinyl ether; Matrix Scientific, CF₂═CFOCF₂CF₂CF₃Columbia, SC PPVE-2 Perfluoropropoxypropyl vinyl ether; Can be preparedCF₂═CFOCF₂CF(CF₃)CFOCF₂CF₂CF₃; ˜90% as cited in U.S. Pat. No. 3,450,684(Darby, Ex 1) VDF Vinylidene fluoride; CH₂═CF₂ Sigma-Aldrich, Milwaukee,WI

Example 1 Preparation of PPVE-2 Homopolymer Dispersion

FLOUROLINK™ C (3.3 g) and potassium hydroxide (0.186 g) were dissolvedin deionized water (90.0 g). To this solution was added NAFION™ SE10172(0.0175 g) and PPVE-2 (50.0 g); the resulting aqueous mixture wassonicated for 60 seconds using a Branson 450 sonifier (available fromVWR Scientific, Bridgeport, N.J.) to produce a coarse emulsion. Theresulting coarse emulsion was then homogenized with a Gaulin 15MRhomogenizer (available from APV, St. Paul, Minn.) at 8800 psi (60.67MPa) with 3 passes to yield an emulsion with a mean droplet size of 144nm. The ensuing fine emulsion was transferred to a 3-neck 250 mL roundbottom flask, fitted with an overhead stirrer and heating mantle. Asolution of deionized water (10.0 g), sodium bicarbonate (NaHCO₃; 0.2 g)and ammonium persulfate (0.2 g) was added to the stirred mixture. Thetemperature of the mixture was then elevated and maintained at 60° C.for 20 hours under a nitrogen blanket. Upon cooling to room temperature,the ensuing homopolymer dispersion (characterized using NMR; 29.1%solids) yield was determined to be 97.9%, with a mean particle size of62 nm as measured on the Horiba LA-910 (Horiba Instruments, Inc, Irvine,Calif.). Monomer conversion to homopolymer was 82%.

Examples 2-4 were prepared essentially according to the procedure forExample 1, with the exception that the conditions and materialsspecified in Table 1 were used. Resulting % solids, mean particle sizeand conversion to homopolymer for Examples 2-4 are also listed in Table1.

Comparative Example C1

Comparative Example C1 was prepared essentially according to Example 1with the exception that the resulting aqueous mixture was notpre-emulsified and duration of the reaction was 24 hours instead of 20hours.

TABLE 1 Mean conversion NAFION ™ Temperature Solids particle to homo- ExSE10172 (g) (C. °) (%) size (nm) polymer (%) 1 0.0175 60 29.1 62 82 2 —60 27.7 62 77 3 0.0175 71 28.4 79 80 4 — 71 15.7 87 41 C1* 0.0175 60 **— — *No pre-emulsification **No reaction observed

Example 5

Example 5 was prepared essentially according to the procedure used forExample 1 with the exception that FLOUROLINK™ C was replaced by PBS, andthe reaction was run at 71° C. for 20 hours. The homopolymer dispersionhad a mean particle size of 230 nm with a conversion of 58%.

Example 6

Example 6 was prepared essentially according to the procedure used forExample 5 with the exception that the addition of NAFION™ SE10172 wasomitted. The homopolymer dispersion had a mean particle size of 157 nmwith a conversion of 24%.

Example 7

Example 7 was prepared essentially according to the procedure used forExample 1 with the exception that PPVE-2 was replaced with PPVE-1. Thehomopolymer dispersion had a mean particle size of 63 nm with aconversion of 48%

Example 8

To deionized water (335.5 g) was added NAFION SE10172 (2.38 g) followedby PPVE-2 (72.0). The ensuing mixture was homogenized using a Gaulin15MR (available from APV, St. Paul, Minn.) at 8800 psi (60.67 MPa) for 3passes, yielding an emulsion which had a mean droplet size of 231 nm. Toan aliquot of this emulsion (341.6 g) was added a solution of deionizedwater (20.0 g) and ammonium persulfate (1.0 g); the resulting mixturewas stirred for several minutes then vacuum charged into a 500 mL highpressure reactor fitted with a stirrer, heating mantle, thermocouple,pressure gauge and gas feed valve. After twice purging with nitrogen andevacuating, the stirrer was set to 800 rpm and the temperature of themixture was brought to 71° C. and maintained for 6 hours.

After 6 hours a 61 wt %/39 wt % VDF/HFP gas mixture was introduced intothe reactor at 150 psi (1034 kPa). The total gas feed time into the 500mL reactor took 3.42 hours. After the gas feed was complete, the reactorcontent was allowed to further react for 2.5 hours. Pressure in thistime period drops from 150 psi (1034 kPa) to about 20 psi (138 kPa). The27.0% solids latex that resulted had a mean particle size of 112 nm.

Example 9

The process for Example 9 is essentially the same as Example 8 with theexception that the first stage polymerization of the PPVE-2 emulsion wasallowed to react for 3 hours instead of 6 hours, and the resulting meanparticle size of the latex was 82 nm (26.8% solids).

Example 10

The process for Example 10 is essentially the same as Example 8 with theexception that the first stage polymerization of the PPVE-2 emulsion wasallowed to react for 0.8 hours instead of 6 hours, and the resultingmean particle size of the latex was 127 nm (26.9% solids).

Comparative Example C2

The process for Comparative Example C2 is essentially the same asExample 8 with the exception that charging of the PPVE-2 emulsion wasimmediately followed by introduction of the VDF/HFP gas mixture, insteadof allowing 6 hours reaction time. The resulting mean particle size ofthe latex was 115 nm (27.7% solids).

TABLE 2 Oil repellency values for Examples 8-10 and Comparative ExampleC2 with varying concentrations on cotton. Hold Time Ex (h) 0.2% SOF 0.5%SOF 1.0% SOF  8 6 1 3 5  9 3 1 3 5− 10 0.8 1− 3− 4 C2 0 0 2 3.5

We claim:
 1. A method of making a bicomponent fluoropolymer dispersioncomprising the steps of: a. pre-emulsifying an aqueous mixture of aperfluorovinyl ether monomer in the presence of a fluorochemicalemulsifier to an average emulsion droplet size of one micron or less,and b. polymerizing said perfluorovinyl ether in the presence of afree-radical initiator at temperature and for a time sufficient toproduce particles of poly(perfluorovinyl other), c. subsequently addingat least one additional fluorinated comonomer without additionalemulsifier, and d. further polymerizing the resulting mixture.
 2. Themethod of claim 1 wherein perfluorovinyl ether monomers are of theformula: CF₂═CF—R_(f) wherein R_(f) represents a perfluorinated organicgroup having a chain length of at least 2 atoms and having at least onecarbon atom and at least one oxygen atom.
 3. The method of claim 2wherein said R_(f) group is a perfluoroalkoxy group, a perfluoroethergroup or a perfluoropolyether group.
 4. The method of claim 2 whereinR_(f) group is of the formula: —O(R¹ _(f)O)_(n)(R² _(f)O)_(m)R³ _(f)wherein R¹ _(f), R² _(f) each independently represents a linear orbranched perfluoroalkylene group having 1 to 6 carbon atoms, R³ _(f)represents a linear, branched or cyclic perfluoroalkyl group having 1 to6 carbon atoms and n and m each independently represents an integer of 0to
 10. 5. The method of claim 4 wherein at least one of n and in isdifferent from
 0. 6. The method of claim 4 wherein in is 0, n is 1, R¹_(f) is —CF₂CF₂—, —CF₂CF(CF₃)— or —CF₂CF₂CF₂— and R³ _(f) represents alinear, branched or cyclic perfluoroalkyl group having 1 to 6 carbonatoms.
 7. The method of claim 1 wherein said fluoropolymer compriseparticles having an average size of 80 to 200 nanometers.
 8. The methodof claim 1 wherein the degree of conversion of said polymerisation insaid first polymerisation step is at least 1 percent.
 9. The method ofclaim 1 wherein the amount of said poly(perfluorovinyl ether) in saidbicomponent particle is from 1 to 50 wt. %.
 10. The method of claim 1wherein the amount of said poly(perfluorovinyl ether) in saidbicomponent particle is from 1 to 10 wt. %.
 11. The method of claim 1producing a bicomponent particle dispersion comprising a firstfluoropolymer consisting essentially of polymerised monomer units of theformula

a second fluoropolymer in said dispersion, wherein R_(f) represents aperfluorinated organic group having a chain length of at least 2 atomsand having at least one carbon atom and one oxygen atom.
 12. The methodof claim 11 wherein a core-shell polymer is produced comprising a coreof said first fluoropolymer and a shell of said second fluoropolymer.13. The method of claim 1 wherein said emulsifier is a salt of linear orbranched perfluoroalkyl carboxylic and sulphonic acids having 4 to 11carbon atoms in the perfluoroalkyl chain.
 14. The method of claim 1wherein said emulsifier comprises perfluoropolymers that compriserepeating units derivable from a monomer of the formula:

wherein a is 0, 1 or 2, and t is an integer of 2 to 4, and G is a moietycontaining one or more nonionic, anionic or cationic hydrophilic groups.15. The method of claim 1 wherein said emulsifier is selected from R_(f)^(a)—O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q¹-COOM orMOOC-Q¹-O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q²-COOZ wherein k, pand q each represent a value of 0 to 15, and the sum of k, p and q beingsuch that the number average molecular weight is at least 200 g/mol,R_(f) ^(a) represents a perfluoroalkyl group of 2 to 4 carbon atoms, Mand Z each independently represent hydrogen or a cation and Q¹ and Q²each independently represents —CF₂— or —CF(CF₃)—.
 16. The method ofclaim 15 further comprising an emulsifier of the formulaMOOC-Q¹-O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q²-COOZ wherein k, pand q each represent a value of 0 to 15, arid the sum of k, p and qbeing such that the number average molecular weight is al least 200g/mol, R_(f) ^(a) represents a perfluoroalkyl group of 2 to 4 carbonatoms, M and Z each independently represent hydrogen or a cation and Q¹and Q² each independently represents —CF₂— or —CF(CF₃)—.
 17. The methodof claim 1 wherein said fluorinated comonomers compriseethylenically-unsaturated fluoromonomer containing at least one fluorineatom substituent on a double-bonded carbon atom, and further substitutedwith a halogen atom, hydrogen, or a lower fluoroalkyl radical.
 18. Themethod of claim 1 wherein said fluorinated comonomers are selected fromtetrafluoroethylene, vinylidene fluoride, hexafluoropropene,chlorotrifluoroethylene, 2-chloropentafluoropropene,tetrafluoroethylene, 1-hydropentafluoropropene,dichlorodifluoroethylene, trifluoroethylene, 1,1-chlorofluoroethylene,and trichloroethylene.
 19. The method of claim 1 wherein said secondpolymerisation step further comprises at least one non-fluorinatedmonomer selected from ethylene and propylene.
 20. The method of claim 1wherein said initiator comprises a water-soluble initiator.
 21. Themethod of claim 20 wherein said water-soluble initiator is present inamounts from 0.01 to 2 weight percent, based on the total weight of themonomers.
 22. The method of claim 1 wherein the temperature of saidfirst polymerisation step is between 50 and 80° C.
 23. The method ofclaim 1 wherein the degree of conversion is said first polymerisationstep is at least 5%.
 24. The method of claim 1 wherein the amount ofemulsifier is from 0.01 to 10 weight percent, relative to the totalweight of the monomer.